For image diagnosis using ultrasonic images, three-dimensional images are generated and displayed based on volume data generated by ultrasonic scanning. As a means for easily generating a desired three-dimensional image, a function of simultaneously setting a viewing direction and a target region (to be referred to as an extraction region hereinafter) for three-dimensional image processing on an MPR image has appeared on the market.
Typically, the above simultaneous setting function displays, in parallel, one three-dimensional image and three MPR images perpendicular to each other. MPR images are displayed to set a viewing direction and an extraction region. The slice positions of MPR images are fixed unless changed by the operator. A three-dimensional image is a two-dimensional display image generated based on a set viewing direction and extraction region.
The following is a procedure for setting operation by the operator for a viewing direction and an extraction region using the above simultaneous setting function. First of all, the operator selects an image, from the three displayed MPR images, which allows easy designation of an extraction region. The operator then moves the mouse cursor onto the selected MPR image, and clicks a mouse button at a position corresponding to one end of an extraction region to designate the start point of a vector (a vector for setting a viewing direction and an extraction region; to be written as a setting vector hereinafter). The operator then moves the mouse cursor to a position corresponding to the other end of the extraction region to designate the end point of the setting vector. The vector connecting the designated start point to the designated end point is set as a setting vector. When the setting vector is set on one MPR image, the projections of the setting vector are displayed on the remaining MPR images. The operator adjusts the three-dimensional direction and length of the setting vector by adjusting the directions and lengths of the setting vectors projected on the remaining MPR images with the mouse cursor.
However, since a setting vector is set on a displayed MPR image, the three-dimensional direction of the setting vector is limited within a slice of the displayed MPR image. For this reason, when the operator wants to direct the setting vector to the outside of the slice of the display MPR image, he/she needs to adjust the slice of the MPR image and re-adjust the direction of the setting vector on the MPR image after adjustment. As described above, in order to optimally set a setting vector in a three-dimensional manner, it is necessary to repeat adjustment of a slice of an MPR image and adjustment of a vector on the MPR image.